A new study has found that inhaling polluted air increases the risk of type 2 diabetes. The latest diabetes study published in the British Medical Journal (BMJ) has re-established pollution as an additional factor responsible for this disease, which was until now mostly linked to lifestyle issues and genetic factors.
This is alarming as pollution has been a chronic issue in India, especially in cities like Delhi, Mumbai and Kolkata, and the close link between air quality and diabetes will worsen the country's growing disease burden and will seriously disrupt the lifestyle-focused diabetes management approaches.
The study done on 12,064 residents of Delhi and Chennai finds a close link between PM2.5 particles and increased blood sugar levels. It found evidence of temporal association between PM2.5 exposure, higher fasting plasma glucose (FPG) and incident type 2 diabetes mellitus(T2DM) in both these urban environments in India, thus highlighting the potential for population-based mitigation policies to reduce the growing burden of diabetes.
The research by leading Indian medical researchers — Dr. Siddhartha Mandal, Dr. Suganthi Jaganathan, Dr. Dimple Kondal, Dr. Joel D Schwartz, Dr. Nikhil Tandon, Dr. V Mohan, Dr. Dorairaj Prabhakaran and Dr. K M Venkat Narayan— provides strong evidence linking short-term, medium-term and long-term exposure to PM2.5, assessed from locally developed high-resolution spatiotemporal models, glycemic markers and incidence of diabetes from a highly polluted region with a high burden of diabetes.
This finding adds to the existing evidence from low-pollution scenarios in the Western population.
Why it is worrisome
“We knew for several years about urban-rural differences in prevalence of diabetes. Till now, these have been attributed to differences in obesity rates, physical inactivity and unhealthy diet, all of which are more common in urban areas. But, this study shows that there could be yet another explanation for the higher prevalence of type 2 diabetes in urban areas. Air pollution could also precipitate diabetes in those who are predisposed to it," warns Dr. V. Mohan, one of the investigators and Chairman, Dr. Mohan’s Diabetes Specialities Centre and Madras Diabetes Research Foundation.
"The conventional thinking is that diabetes is largely due to unhealthy diet, low physical activity, obesity with some individuals having a higher genetic risk, but this study brings into focus air pollution as a cause for diabetes among Indians," confirms another investigator Prof. Dorairaj Prabhakaran, Executive Director, Centre for Chronic Disease Control, and a Distinguished Professor of Public Health, Public Health Foundation of India,
Establishing these links using data from a long-term cohort study within the Indian population is crucial to understand the real effects of pollution on health. And, we hope this would lead to further national scale research as well as incorporation of these findings in forming policies and air-quality standards for the country," added Siddhartha Mandal Senior Research Scientist at Center for Chronic Disease Control, who was also part of the study.
Epidemiological evidence linking particulate matter with type 2 diabetes mellitus (T2DM) suggests increased risk of diabetes, an increase in intermediate risk factors like Homeostatic Model Assessment for Insulin Resistance (HOMA-IR), insulin, fasting plasma glucose (FPG) and glycosylated haemoglobin (HbA1c),11 and increased diabetes-associated mortality.
It is known that PM 2.5 particulate matter can produce not just respiratory problems, but they also act as endocrine disruptors. In the case of diabetes, they can lead to reduced insulin secretion from the pancreas as well as produce insulin resistance the liver and muscle, the two primary pathophysiological defects in type 2 diabetes.
The study results suggest a close link between long-term exposure to ambient PM2.5 and T2DM, which may have potential public health significance as well as policy implications for India, a country with high levels of ambient pollution as well as high burden of cardiovascular and cardiometabolic diseases.
Developing diabetes
Type 2 diabetes is a major public health concern. Several studies had earlier found an increased diabetes risk linked with exposure to air pollution.
The burden of diabetes is high and increasing globally, and in developing economies like India, mainly fueled by the increasing prevalence of overweight/obesity and unhealthy lifestyles.
According to the most recent study by India's ICMR in collaboration with Madras Diabetes Research Foundation , the country has 101 million people living with diabetes and another 136 million people are already in pre-diabetes stages.
Approximately 57% of these individuals in India remain undiagnosed. Type 2 diabetes, which accounts for the majority of the cases, can lead to multi-organ complications, broadly divided into microvascular and macrovascular complications. These complications are a significant cause for increased premature morbidity and mortality.
The prevention and management of diabetes and associated complications is a huge challenge in India due to several issues and barriers, including lack of multisectoral approach, surveillance data, awareness regarding diabetes, its risk factors and complications, access to health care settings, access to affordable medicines, etc.
There is evidence that type 2 diabetes in children and adolescents is increasing in some countries. With increasing levels of obesity and physical inactivity among children and adolescents in many countries, type 2 diabetes in childhood and adolescence has the potential to become a global public health issue.
A Lancet study –India State-Level Disease Burden Initiative Diabetes Collaborators—showed that the prevalence of diabetes increased in every state of India from 1990 to 2016 with 2.5 times variation in prevalence across the states in 2016. The highest prevalence was found in the south Indian states of Tamil Nadu and Kerala, and followed by Delhi, Punjab, Goa and another southern state— Karnataka.
The increase in both the prevalence and death rates from diabetes points to possible shortfalls in the management of diabetes like delayed diagnosis and failure to screen for early-stage complications.
But it also gives hope that an effective pollution control can help control diabetes as well.
"While this new finding is worrisome, it also gives hope that by controlling pollution at least to some extent the soaring diabetes epidemic in India can be arrested. Urgent steps have therefore to be taken to control pollution, particularly in our large cities,” Dr Mohan says.
Limited landscape
The BMJ study has made an attempt to assess the association between long-term air pollution on diabetes occurrence. Such studies of long term exposures to air pollution relies on databases or on cohort studies.
However, the study has its own set of limitations in terms of general application, exposure assessment, or the ability to differentiate incidence and prevalence cases.
Firstly the results are based on a cohort located in two urban environments in India, which limits the generalisability of the results across the country. Specifically, the rural population in India is exposed to different levels of ambient as well as indoor pollutants along with varying socioeconomic status and dietary practices, which were beyond the scope of this study.
Further, lack of quantified indoor PM2.5, which also exists in urban environments, is a limitation in the study. There are also no detailed exposure assessments for other pollutants such as nitrogen dioxide (NO2), which might also play a role in impaired glucose metabolism.
(Edited by : C H Unnikrishnan)
First Published: Nov 2, 2023 9:34 AM IST
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